package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;


@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
//        Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
//        Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);
        Shop shop = cacheClient.queryWithMutex(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
        if (shop == null) {
            return Result.fail("店铺不存在！");
        }
        return Result.ok(shop);
    }

    //缓存穿透
    public Shop queryWithPassThrough(Long id) {
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是空值
        if (shopJson != null) {
            return null;
        }

        //4.不存在，根据id查询数据库
        Shop shop = getById(id);
        //5.不存在，返回错误
        if (shop == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }

    //缓存击穿
    public Shop queryWithMutex(Long id) {
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中的是否是空值
        if (shopJson != null) {
            return null;
        }

        //实现缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判断是否获取成功
            if (!isLock) {
                //4.3失败，则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            if (StrUtil.isNotBlank(stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id))) {
                //3.存在，直接返回
                return JSONUtil.toBean(stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id), Shop.class);
            }
            //4.4成功，根据id查询数据库
            shop = getById(id);
            //模拟重建的延时，高并发
            Thread.sleep(200);
            //5.不存在，返回错误
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
            //6.存在，写入redis
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unlock(lockKey);
        }

        //8.返回
        return shop;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.MINUTES);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空！");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存(如果删除操作有异常，整个事务要回滚，保证原子性)
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return null;
    }
}
